I am conceptualizing a product and think I may be approaching some fundamental physical limits, but as I am a biochemist by training my knowledge of physics is not very robust. Here is a basic overview of what I am trying to do: I would like to have a very narrow channel (perhaps as narrow as 2 nm, though it may be practical to have it as wide as 20 nm and if physics requires it may be possible to go as wide as 100 nm) through which I will shine UV light. I am interested in the wavelengths from 230 - 280 nm and would like to get a spectra. I am guessing it may be necessary to have the slit be a minimum of 280 nm long else no light waves would get through at all. I also speculate the light would be polarized by the passage. My dim understanding of diffraction makes me think that the light that does make it through the slit would be spread in an even hemisphere as opposed to a single line, which would make the eventual detection a challenge because of the small amount of light actually reaching a detector. To additionally compexify matters, I would like to be able to measure the spectra emitted by the slit as often as a billion times a second (though a prototype would be fine if it worked at 1,000 times a second) further dramatically reducing the number of photons at each measuring event. What I am hoping I can get from the readers here is some pointers on how realistic my aims are, if I am past the bleeding edge of science or if what I am attempting to do is physically possible. If you readers are feeling generous, perhaps you can point me to relevant research that shows I am a bonehead or might have a chance (depending where on the bleeding edge I am).

What I believe will be required is the ion beam etching of a metal coated quartz slide to create the channel/groove/slit. Then a deuterium lamp to provide the UV light to shin through the slid. On the other side of the slide I would have to have a diffraction grating tuned to the UV range reflecting light to some sort of photomultiplier sensitive to the UV then some sort of camera to capture the amplified light that is capable of capturing frames at a high rate. Other than getting my noggin around the amount of light that might make it through the slit and what would happen to it once it reaches the other side, there does not appear to be any huge challenge in accomplishing any of these goals. However, if the number of photons that make it through the slit are below a certain point (I probably need to have at minimum 100 photons from each spectral band (I probably only need 10 nm resolution) per collection time period in order to have a clear signal to noise ratio) then the fact that the rest is physically possible is moot.

Thank you all for your time!

Just suggestions, based on your requirements.

Your detection rate (billions/sec or even thousands/sec) can only be met with a pulsed source.

To scale up the number of photons/pulse you need to increase your fluence or power.

Why is the slit so small? Subwavelength apertures do not linearly transmit light anymore. Usually these are used for special cases in the near field where the light for example is converted to plasmons right after leaving the aperture.

The reason for the narrow slit is proprietary, but it is integral to the success of the concept. Are you implying that it is not possible to accomplish what I described? In the long run I would position the diffraction grating and detectors much closer (sub millimeter); is that going to be necessary for a prototype as well to have any chance of success?

Why the need for a pulsed source? If I use a simple CCD camera as my detector I should be able to read the results from the camera at whatever rate the camera supports, right?

Thanks for your input!

Sure if you have GHz electronics you can read it as fast as you want. A pulsed source just seemed more natural (to me) because it would already be integrated.

But as for the small slit, it will not even diffract (far field sense) if it is sub-wavelength. Your slit spec is less than half-wavelength, which won't even allow guided wave modes in the slit.

But if you can use near field information, there is lots of opportunity. The trouble is then the distance of your detector from the slit must also be sub-wavelength.

You can use something like a SNOM as the detector. It can scan the slit region very close and pick up the near field image.

So 'near field' is sub wavelength distance? I guess I was thinking that milimeter would be 'near'. Would the distance from the slit to the detector have to be the same as the width of the detector? If the slit width is 2 nm how far away do you think I can put the detector?

What is SNOM? Scanning Near-Field Optical Microscope? I saw one machine that appeared to work at 100 microns; do you think that would work in my case?

I might be able to alternate wavelengths rather than attempt to get a spectra (I could probably compare just two wavelenghts to get the information I need). Obviously it will reduce my maximum reading rate but if it will make it possible vs impossible then that will have to be the way it is done.

Thanks again for your input!

SNOM looks like a surface scanning technique (at least according to Wikipedia). I am not particularly interested in resolution (at least along the narrow width of the slit; along the length of the slit I would like to be able to resolve things, but I could easily have a slit that is a millimeter long and target micrometer resolution), just being able to measure the relative intensity of the different wavelengths. If I go to alternating wavelengths (i.e., the light entering the slit is of a narrow range of wavelengths (perhaps over 5-10 nm (are there single wavelength sources for, say, 230 and 260 nm?)) so I don't need spectrum, does that simplify matters? I am starting to get the impression that I may be asking for something that may be beyond the physical limits. Is that the case or do you think I can achieve my goal, with some compromises?

The subwavelength slit will not let light travel more than a fraction of a wavelength away from it. There is exponential decay.

Your detection scheme is otherwise fine, and everything would be great if your wavelength were smaller than the slit.

In the near field case, probably stationary (optional scanning) near-field optical microscope would be good enough for your wavelength-to-wavelength comparison.